Sound-amplifying device



H. W. THAYER April 8, 1930.

SOUND AMPLIF'YING DEVICE Filed Oct. 10, 1928 2 Sheets-Sheet M A TTORN EY$ Paaad Apr. 8, 1930 UNITED STATES PATENT OFFICE SOUND-AMPLIFYINGDEVICE Application filed October 10, 1928. Serial No. 811,450.

This invention relates, generally, to improvements in sound amplifyingdevicesof. the type shown and described in my United States LettersPatent No. 1,701,515, dated February 12, 1929; and this invention hasfor its principal object to provide an improved construction of -coupledvibratory diaphragms spaced apart to furnish an intermediate resonancechamber having sound wave outlets.

This invention has for a further object to provide a novel maindiaphragm structure having in combination therewith substantially radialdistributing ribs adapted to uniformly disperse the vibratory impulsestransmitted thereto substantially throughout the entire area of thediaphragm member, and especially toward the outer limits orcircumference thereof, whereby a more uniform excitation of the body ofair in contact with the diaphragm surface within the resonance chamberof the device is obtained, to the end that a more efficient regenerationof sound waves is attained with a resultant better and more faithfultonal quality of the reproduced sound.

Other objects of this invention, not at this time more particularlyenumerated, will be clearly understood from the following detaileddescription of the same. 7

The invention is illustrated in the accompanying drawings, in which:-

Fig. 1 is a front face view of one'form of coupled vibratory diaphragmsspaced apart to furnish an intermediate resonance chamber having soundwave outlets, and embodyingthe improvements according to this invention;Fig. 2 is a vertical cross sectional view of the same; Fig. 3 is aninside face view of the main diaphragm showing one form of thedistributing rib structure with which the same is provided; and Fig. 4is a fragmentary detail section, taken on line 4- 1 in said *Fig. 3.

Fig. 5 is a fragmentary inside face view of the main diaphragm, showinga modified arrangement of distributing rib structure; and

Fig. 6 is a sectional view of same, taken on line 66 in Fig. 5.

Fig. 7 is a fragmentary inside face view of the main diaphragm, showinganother modified arrangement of distributing rib structure; and Fig. 8is a sectional'view of the same, taken on line 88 in Fig. 7.

Fig. 9 is a fragmentary inside face of the main diaphragm, showing stillanother modified arrangement of distributing rib structure; and Fig. 10is a sectional view of the same, taken on line '1010 in Fig. 9.

Figs. 11 and 12 are respectively additional fragmentary inside faceviews .of. the main diaphragm with further modified arrangements ofdistributing rib structure.

Similar characters of reference are employed in the said drawings toindicate corresponding parts.

In the drawings the amplifying device is shown as comprising a maindiaphragm 15 connected by its marginal portions to a forwardly facingsupporting ring 16, a forward diaphragm 17 connected by its marginalportions to a rearwardly facing supporting ring 18; said diaphragmsbeingaxially ali ed and spaced apart, to provide an interme iateresonance chamber 19, by means of radial spacer blocks 20 insertedbetween the supporting rings 16 and 18 and secured thereto, all so thatopen spaces are provided between said spacer blocks 20 adapted to leadoutwardly from the interior of said resonance chamber, thus providingsound wave outlets for the latter. If desired, the rearward or maindiaphragm 15. may be of rearwardly directed concavo-convex conformation,while the forward diaphragm may be of forwardly directed concavo-convexconformation.

Preferably said forward diaphragm 17 is centrally reenforced by areenforcing disc 21 of reduced diameter, which is adhesively securedtothe inner face thereof, although I do not intend to limit myself to suchconstruction or arrangement.

Secured to the inner or forward face of said rear diaphragm 15 by anysuitable means, but preferably by a stron adhesive such as glue, are aplurality of distributing ribs disposed to radiate from the centralpoint of the diaphragm toward the periphery thereof but terminatingshort of the supporting ring 16 and within the effective limits of theties.

vibratory body of said diaphragms. These ribs may be made of anysuitable material, suchas wood, fibre, pyroxylin, etc., and arepreferably of tapering form. diminishing in size or thickness towardtheir outer extremi- Means for coupling to the diaphragm 15 thetransmission rod 22 of a telephonic receiving unit or other desired formof vibratory reproducer (not shown) is provided. Said means comprisesaperforate internally threaded disc 23 centrally secured to the diaphragm15 in connection with the distributing ribs thereof. Threaded into saiddisc is the externally threaded shank 24 of a rearwardly projectingcoupling socket 25, in which the end of said transmission rod 22 may beinserted and thereupon secured by a set screw 26 so that the vibrationsof the telephonic receiving unit or other vibratory device may beoperatively transmitted to said diaphragm 15. The forward diaphragm 17is coupled With the main diaphragm 15, so as to be positively andsynchronously vibrated therewith, by means of a coupling or connectorpiece 27 which maybe retained in place by the inherent opposing stressesof the diaphragms 15 and 17, or which, if desired, may be mechanicallysecured as by glue or other fastening means to the central portion ofthe main diaphragm rib structure and at the other end by glue or otherfastening means to the inner side of said diaphragm 17. Said coupling orconnector piece 27 may be made of any substantially ri id material. Ihave found cork to be especially suitable for the purpose since it isboth rigid enough to transmit vibratory effects while nevertheless isslightly resilient so that any tendency to the production of metallictimbre in the machanical vibration of the diaphragm is avoided.

There are a variety of specificall different forms and arrangements ofdistri uting rib structure which may be satisfactorily employed inconnection with the diaphragm 15. In the accompanying drawings I haveshown several such forms and arrangements which are. illustrative of theprinciples of construction involved in and which are all within thescope of this invention.

Referring to Figs. 1 to 4 inclusive,-I have therein shown onearrangement of distributing ribs, comprising pairs of parallel spacedrib members 28 disposed at right angles.

center blockbeing firmly secured to the rib members by glue or othersuitable fastening means. Said center block serves as a point .ofattachment for one end of the coupling or connector piece 27, wherebythe forward diaphragm 1 is operatively coupled with the diaphragm 15 andits rib structure so as to vibrate synchronously therewith.

In Figs. 5 and 6 I have shown another simple form and arrangement ofdistributing rib structure, comprising single rib members 30 of integralform arranged at right angles one to the other and extending from sideto side of and securely afiixed to the diaphragm 15, the same havinginterfitting central mortised portions 30 at their points ofintersection. These rib members 30 are cut away at their-inner centralportions, as indlcated at 31, to straddle the disc 23. Preferably theintersecting central portions of these rib members 30 areoutwardlyprojegted as shown to provide a point of attachment for one endof the coupling or connector piece 27, whereby the forward'diaphragm 17is operatively coupled with the diaphragm 15 and its rib structure tovibrate synchronously therewith.

In Figs. 7 and 8 I have shown another modified arrangementvofdistributing rib structure, which comprises the provision ofv a centralrectangular block 32 superimposed on the disc 23, and to the respectivesides of which are secured, by glue or other suitable fastening means,rib-arms 33 adapted to extend outwardly from said block 32 toward themarginal portions of the diaphragm 15, said ribarms 33 being securelyafiixed to the inner face of the latter. The coupling or connector piece27 is mounted between the forward diaphragm 17 and said central block32.

In Figs. 9 and 10 I have shown a. still further modified arrangement ofdistributing rib structure, the same consisting in a hub block 34superimposed on the disc 23, and mortised into said hub block 34 are theradiating rib members 35, which extend therefrom toward the marginalportions of the diaphragm 15, and which are also securely affixed to theinner face of said diaphragm. The coupling or connector piece 27 ismounted between the forward diaphragm 17 and said hub block 34.

In Fig. 9 I have shown four radial rib members 35 spaced ninety degreesapart; it will be obvious, however, that more or less than four ribmembers may be utilized. For example, in Fig. 11 I have shown six suchradial rib members, and in Fig. 12 eight such radial rib members,equi-spaced around the inner face of the diaphragm 15. i

In the operation of the amplifying device,

the telephonic receiver 'or other vibratory transmlssion unit transmits,through the rod '22, the vibrations to the central part of the I withwhich the diaphragm 15 is provided tends to radially disperse thevibratory impulses uniformly throughout the entire area of the diaphragm15, with the result that the body of air within the resonance chamber ismore efliciently excited and the tonal quality of the sound reproducedis greatly improved.

- In general the operation of the coupled diaphragms providing theresonance chamber is the same in principle and effect as that describedin my copending application Ser. No. 233,793, filed November 17, 1927,and already above referred to, in the instant species the forwarddiaphragm 17 being interconnectedthrough the coupling orconnector, piece27 so as to partake of the vibrations trans mitted to the reardiaphrag1n15, whereby the two diaphragms vibrate in synchronism withexciting effect on the air within the resonance chamber 19 and resultantdispersion of sound -waves through the, marginal outlets with which saidresonance chamber is provided.

. As many changes, other than those already indicated, could be made inthe above described construction, and 'many apparently widely differentembodiments of this invention could be made without departing from thescope thereof, it is intended that all matter contained in the abovedescription or shown in the accompanying drawings shall be interpretedas illustrative and not in a limiting sense.

I claim 1. In a sound amplifying device comprising a plurality offspaceddiaphragms centrally coupled for synchronous vibration and so as toprovide resonance space therebetween having sound wave outlets adjacentto the margins of the diaphragms, a plurality of uniformly spaceddistributing ribs aflixed to the inner face of one of said diaphragms toradiate from itscentral portion toward butshort of the margins thereofso as to vibrate therewlth, said ribs being of tapering formationtoward, their outer extremities, and means connected with said latterdiaphragm for transmitting to said diaphragms vibratory motion of theorder of sound wave fre quencies. 1

2. In a sound amplifying device, a pair of diaphragms in axial alignmentand spaced apart to provide a resonance chamber, peripheral'rings tosupport the marginal portions of said diaphragms, spacing meansintermediate and to which said rings are secured and disposed to providetherebetween sound wave outlets leading from said resonance space, aplurality of distributing'ribs afiixed to the inner face of one diaphram to radiate from its central portion towar but short of the marginsthereof so as to vibrate therewith, means to couple said diaphragms forsynchronous vibration, and means connected with said rib-provideddiaphragm for transmitting to both said diaphragms vibratory motion ofthe order of sound wave frequencies.

'3. In a sound amplifying device, a pair of diaphra ms in axialalignment to provide an of said forward dia hragm, and means to.

centrally couple sai diaphragms for synchronous vibration.

4. In a sound amplifying. device, a pair of diaphragms in axialalignment to provide an intermediate resonance space, a peripheralsupporting frame structure intermediate and to which the margins of saiddiaphragms are secured, said frame structure being provided with soundwave outlets leading from said resonance space, the forward diaphragmbeing of forwardly projected concavo-convex form, means to reenforce thecentral portion of said forward diaphragm, the rearward diaphragm beinof rearwardly projected concavo-convex orm, a plurality of distributingribs affixed to the inner face of said rearward diaphragm to radiatefrom its central portion and so as to vibrate therewith, and means tocentrally couple said diaphragms for synchronous vibratlon.

5. A sound amplifying device. as defined q in claim 4, in which saiddistributing ribs are provided with a tapering formation tothis 6th dayof October, 1928.

HENRY w. THAYER.

